Let's get this math done. We have 321 and we're going to multiply it by 5. This is the same as taking 321 and adding it to itself 5 times.
Step 1: 0 + 321 = 321
Step 2: 321 + 321 = 642
Step 3: 642 + 321 = 963
Step 4: 963 + 321 = 1284
Step 5: 1284 + 321 = 1605

So, 321*5 = 1605